Article 1. In this Notification, the terms and definitions given in the
(1) Enclosure an enclosure which is requisite for maintaining
explosion-protection properties of electrical equipment, such as external
casings, external coverings, protective covers, etc.
(2) Surface joint place where corresponding surfaces of parts of
an enclosure of electrical equipment come together, with a gap having a
passage from the inside of the enclosure to the outside
(3) Type of gas-explosion protection "Flameproof enclosure" type of protection applied to an enclosure which
can withstand internal explosion pressure and prevent the ignition of flammable
gases (hereinafter referred to as gases) or ignitable vapours (hereinafter
referred to as vapours) surrounding the enclosure by the flame of explosion,
when gases or vapours enter the enclosure and cause an internal explosion.
(4) Type of gas-explosion protection "Pressurized enclosure" type of protection applied to an enclosure, the
ingress of external gases or vapours into which is guarded by supplying
or enclosing a protective gas, such as air, nitrogen, carbon dioxide, etc.
(5)Type of gas-explosion protection "Increased safety" type of protection applied to parts(excluding
non-current-passing parts) of electrical equipment, which, during normal
service or under normal current-carrying conditions, do not cause arcs
or sparks or high temperatures capable of becoming an ignition source and
to which an increased degree of safety is provided in terms of insulation,
temperature-rise, mechanical damage from the outside, etc.
(6) Type of gas-explosion protection "Oil-immersion" type of protection in which parts of electrical
equipment, which can cause sparks or arcs or high temperatures capable
of becoming an ignition source, are immersed in an insulating oil, and
thus preventing the ignition of gases or vapours
(7) Type of gas-explosion protection "Intrinsic safety" type of protection in which any sparks, arcs or
heat occurring in parts of electrical equipment have been confirmed by
tests, etc. that they are incapable of causing the ignition of gases or
(8) Type of gas-explosion protection "Special" type of protection applied to electrical equipment,
other than those defined in the above (3) through (7), and the explosion-protection
properties of electrical equipment against gases or vapours are confirmed
by tests, etc.
(9) Type of dust-explosion protection "Ordinary enclosure" type of protection in which an enclosure is so
constructed that outside dusts find it difficult to enter the enclosure
by providing surface joints with a gasket, or by making the width of surface
joints longer and so forth, and in which temperature-rise of the enclosure
is limited so that the ignition of flammable dusts (except for explosive
dusts) outside the enclosure does not occur
(10) Type of dust-explosion protection "Special enclosure" type of protection in which an enclosure is so
constructed that dusts outside the enclosure are prevented from entering
the enclosure by providing surface joints with a gasket, etc. and in which
the temperature-rise of the enclosure is limited so that the ignition of
explosive dusts outside the enclosure does not occur by limiting temperature-rise
of the enclosure
(11) Gap maximum distance between the corresponding parts
or surfaces of a joint, or maximum difference between the diameters of
the bore and the cylindrical component, when the inside of electrical equipment
is below the atmospheric pressure
(12) Width of joint shortest path through a joint corresponding to
the gap when the gap is maintained at or less than the allowable value
given in para.1, Article 7 and Article 8, respectively
(13) Explosion class degree of ignitability of gas or vapour, classified
according to the minimum distance between the corresponding surfaces of
a joint of the test enclosure when the explosion test is conducted and
a flame propagation occurs to the exterior (hereinafter referred to as
" flame propagation limit" )
(14) Ignition group degree of flammability of gas or vapour according
to the value of the ignition point
(15) Shrouding structure applied to parts surrounding the heads
of screws fastening an enclosure of electrical equipment where the screws
are incapable of being loosened without special tools
(16) Creepage distance shortest distance along the surfaces of insulating
materials between a bare live part and other parts which shall be insulated
from the bare live part
(17) Clearance shortest distance through air between a bare live
part and other parts which shall be insulated from the bare live part
Article 2. Electrical equipment under the provision of para.1, Article
280 of the Ordinance on Industrial Safety and Health (the Ministry of Labour
Ordinance No.32, 1972) (hereinafter referred to as "the Ordinance")
shall be of protection 'flameproof enclosure' type, 'pressurized enclosure',
'increased safety', 'oil immersion', 'intrinsic safety' or 'special'.
2. Electrical equipment under the provision of para.1, Article 281 of the Ordinance shall be of dust-explosion protection type 'ordinary enclosure' or 'special enclosure'.
3. Electrical equipment under the provision of para.1, Article 282 of the Ordinance shall be of dust-explosion protection 'special ' type.
Article 3. Electrical equipment shall be so constructed that it is easily inspected and repaired; and the materials used shall be electrically, mechanically, thermally and chemically durable.
Article 4. Electrical equipment shall attach to easily visible part with
label which indicates the following items:
(1) Type of (gas- or dust-explosion) protection: Electrical equipment integral
with two or more types of protection may indicate only a type of protection
applied to the main body of electrical equipment, except when necessary
for proper handling or securing safety.
(2) Explosion class (only for 'flameproof enclosures' ) and ignition group: Where gases and vapours are specified, the indication of explosion class and ignition group may be omitted by instead indicating their names.
(3) Ratings of circuits in electrical equipment of protection type 'intrinsic safety' or 'special ' and the essential points of conditions of use:
2. Type of protection, explosion class and ignition group shall be indicated by the symbols shown in the following tables, respectively:
(1) Kind of type of protection
|Kind of type of protection
(2) Explosion class
|Limit of flame propagation (mm)
|Over 0.4 and not more than 0.6
|Equal to or less than 0.4
||3(3a 3b 3c 3n)
|Note: 3a, 3b, 3c and 3n denote water gas, carbon disulfide, acetylene and
all gases and vapours, respectively.
(3) Ignition group
|Ignition point (degree)
|Over 300 and not more than 450
|Over 200 and not more than 300
| Over 135 and not more than 200
|Over 100 and not more than 135
3. Despite the provisions of the two preceding paragraphs for electrical equipment which is considered to be in conformity with the provisions of Chapter 2 (excluding Section 6) through Chapter 4, based on the following Article, the method of the indication according to the two preceding paragraphs may be that approved by the Director-General of the Labour Standards Bureau, the Ministry of Health, Labour and Welfare.
Article 5. Among electrical equipment not in conformity with the provisions
of Chapter 2(excluding Section 6) through Chapter 4 (hereinafter referred
to as the provisions in this Article), that in which special materials
are used or special configurations are adopted, or which is used in special
locations, or which is manufactured on the basis of the international standards
relevant to the provisions and confirmed by tests, etc. to be equivalent
in explosion-protection properties to that in conformity with the provisions,
is deemed to be in conformity with the provisions.